06/12/2026
Not all synthetic oils are created equal.
Many racers and engine builders assume that because two products are labeled "synthetic," they will automatically work well together. In reality, synthetic oils can be formulated with very different base stocks, additive chemistries, and anti-wear packages.
Blending different brands or formulations can dilute the protection or performance characteristics that each manufacturer engineered into the product. This can be especially important in high-performance, racing, or break-in applications where maximum protection is critical.
When changing from one oil brand to another, consider these best practices:
✅️ Drain the engine thoroughly while the oil is at operating temperature.
✅️ If possible, add the new oil and briefly circulate or drain it to help flush out residual oil from the previous formulation.
✅️ Replace the oil filter, if applicable, to minimize residual oil from the previous formulation.
✅️ If practical, inspect the old oil, filter, or seals and gaskets for signs of contamination or abnormal wear.
✅️ Avoid topping off with a different brand or formulation unless necessary.
✅️ Give the new oil a complete service interval to establish its intended additive chemistry throughout the engine.
For the highest level of consistency and performance, we recommend using a complete lubrication system from a single manufacturer. FHS Oil products are engineered to work together—from Assembly L**e to Break-In Oil to Racing Oil—providing a consistent additive strategy throughout the life of your engine build.
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